1. Field of the Invention
The invention relates to apparatus for coupling a multiple-ringing patterns capacity telephone line to a telephone line subscriber device when a particular ringing pattern is present on the telephone line. More particularly, the invention relates to such apparatus wherein the particular ringing pattern includes at least two rings, and the second ring occurs within a predetermined time interval after the first ring.
2. Description of Prior Art
Devices exist which allege to permit facsimile terminals to share a telephone line with other uses, for example, with a telephone instrument. However, these devices do not provide a second telephone number. Typically, the prior art devices depend on the presence of a "fax tone" which is actually a "calling non-speech device" tone and is missing in a substantial number of facsimile terminals presently in use. Other devices rely on delay, and assume that a human will pick up a telephone receiver after three to five rings, and, after a delay, switch to the telefacsimile terminal.
There are, however, systems which do share a single line between at least two telephone devices such as, for example, a telephone instrument and a telefacsimile terminal. Two such systems are described in U.S. Pat. Nos. 4,578,534, Shelley, Mar. 25, 1986 and 4,825,465, Ryan, Apr. 25, 1989.
In the '534 patent, the non-dedicated telephone line 20 can be connected-either to a data set 10 or a telephone instrument 40 through contacts a, b and c of relay 61. When a computer is to access the data set 10, it sends a single ring burst. On receipt of this single ring burst, contacts a and b remain connected and the system dials the telephone number of the computer. When an external party wishes to reach the telephone instrument, the telephone number of the instrument is dialed. On the second ring burst, contact b will mate with contact c by action of the relay 61 so that the telephone instrument is connected to the telephone line 20. The system does not use two telephone numbers, including the coded telephone number, as in the inventive system.
In the '465 patent, a controller 10 consists of two parallel circuits 26 and 28 (see FIG. 2 of the Patent). Circuit 26 comprises a relay L.sub.1 having coils 30 and 32 and operating contacts 38 and 40. Circuit 28 comprises a relay L.sub.2 having coils 34 and 36 which operate contacts 42 and 44. Circuit 26 connects a telephone line to a device 12 (a PBX), while circuit 28 connects the same telephone line to a device 14. (a telefax machine). When one of these devices is in the off-hook condition, current will flow through the coils of its relay to thereby disconnect the other device from the telephone line so that only one device is connected to the telephone line at a time. For example, if the telephone receiver of the PBX is lifted off the hook, current will flow through coils 30 and 32 so that contacts 38 and 40 will disconnect. Thus, only the telephone device will be connected to the line 18.
In both of the patented devices, only a single telephone number is used to access either the telephone instrument or a second telephone device. Thus, the feature of automatically being connected to the telefax or the receiver as a function of the telephone number dialed is not included in, nor would it be obvious from, the teachings of the selected references.
Also known in the art are U.S. Pat. No. 4,807,278, Ross, Feb. 21, 1989, U.S. Pat. No. 4,998,273, Nichols, Mar. 5, 1991 and U.S. Pat. No. 5,142,569, Peters et al, Aug. 25, 1992.
The Nichols patent teaches an arrangement for automatically connecting a telephone line to a facsimile or other telephone connected device upon sensing a predetermined ringing pattern. However, there are substantial differences as between Nichols and the teachings of the present application as will be discussed below.
Ross simply teaches a device including two separate circuits for connecting a telephone line to two separate devices wherein each circuit senses current flowing in the other circuit indicating that the other circuit is in use and preventing the use of the circuit which senses the use of the other circuit.
Peters et al also teaches an apparatus for coupling a multiple ringing patterns capacity telephone line to a telephone line subscriber device when a particular ringing pattern is present on the telephone line. However, as stated at column 6, lines 60 et seq. of the Peters et al patent, the sensing circuitry comprises a timing logic circuitry which examines all of the pulses of the ringing pattern and compares it with patterns stored in detectors 111, 113 and 115. Thus, the entire ringing pattern has to be played out in order to determine which ringing pattern is present on the telephone line.
In addition, the multiplicity of detectors needed in Peters et al for the detection of the full ringing pattern, taken together with a reliance on a "normally energized" relay logic, precludes the use by Peters et al of telephone line power alone.